In Gourlandt et al, U.S. Pat. No. 3,964,481, issued June 22, 1976, which is incorporated herein by reference, there is described an automatic injection device for injecting a liquid, such as a vaccine or medicine, into an animal retained or held in position on an outer portion of the device. The particularly described apparatus has an electrically operated motor for mechanically driving an injection syringe. The U.S. Pat. No. 3,964,481 states that a fluid-pressure motor could be used. This apparatus provides the means for vaccinating at least about 2000 chicks per hour while at the same time ensuring that an accurate dosage, on the order of one part in one hundred, is injected at an exact location on the animal.
Very often, the automatic injection device of U.S. Pat. No. 3,964,481, referred to above and hereby incorporated by reference, is used at locations remote from electrical power. Under these circumstances, it is desirable to provide a totally fluid driven apparatus, as is provided for in the U.S. Pat. No. 3,964,481; that is, an apparatus which requires no electrical power and which provides the convenience, speed of operation, and precision of the electrically powered device. Such pneumatically controlled apparatus are not only described and claimed in the U.S. Pat. No. 3,964,481, but in addition, at least one United States manufacturer has marketed a pneumatically controlled and operated machine.
A totally pneumatically controlled and actuated machine, however, presents some problems from a practical commercial viewpoint. Without the availability of electrical power, the machine must rely on gas powered devices to perform all of its operating functions. Thus, for example, in order to warn the operator that a predetermined or selected number of chicks have been vaccinated, it is typical to provide a gas operated whistle as the warning signal. Such signals however may cause some confusion and instill fright in the animals being vaccinated. This is, of course, an undesirable side effect.
In addition, a totally pneumatic machine presents some difficulty in cleaning since the mechanical and pneumatically connected portions are often difficult or cumbersome to disconnect and disassemble. Furthermore, it is particularly important to have the retention means described in the U.S. Pat. No. 3,964,481 available and easily removable for cleaning, because this portion of the apparatus is likely to require more frequent routine maintenance than the other portions of the apparatus which are fully enclosed within the apparatus housing.
It is necessary also, in the earlier described pneumatic systems, to provide careful inspection of the pneumatic drive system since the forces and stresses arising in the pneumatic system are often greater than the forces and stresses arising in the corresponding electrically driven systems.
Principal objects of this invention are therefore to provide a pneumatically operated injection apparatus having a modular construction, and in particular, wherein the retention means may be quickly and easily disconnected, both mechanically and pneumatically, from the rest of the apparatus; wherein a silent signaling means is provided to signal the termination of a series of injections; and wherein means are provided to reduce the wear and stresses on the driven mechanical components of the pneumatic system. Further objects of the invention include providing a pneumatically operated injection apparatus which is reliable, which has a minimum number of moving parts, which can be easily disassembled, which has a minimum cost, which provides accurate and precise positioning of the animal part to be injected, which provides an accurate dosage during injections, which is portable, and which can be reliably operated by unskilled personnel.